Several commercial and industrial buildings can reach heights of over 60 stories. Apparently, when these buildings are being constructed, they require equally tall cranes to transport the materials to the higher floors. There are cranes that are operated from the rear of trucks or other types that have their own vehicle attached. Tower cranes are the largest types on the market.
Tower cranes are stand-alone structures seen as part of a major city's downtown skyline on high-rise building projects. Wherever new construction such as apartment buildings and skyscrapers and commercial facilities such as shopping center are being constructed, odds are a crane will be on site.
Kinds
There are two different kinds of cranes: jib crane of the boom crane. The jib is a metal frame which extends from the main section. On a flat tower crane, the jib remains horizontal as it lifts items. On a luffing kind of tower crane, the jib could ratchet to upward or downward angles. The lifting capacity for both kinds can vary from 30,000 lbs. to 10,000 lbs.
Body
The body of the crane is composed of a vertical steel mast that is composed of individual sections. The sections are added to increase the overall height of the equipment. The mast extends upward to wherever the desired height is, to the control module, which is a small room that has glass windows on all four sides or to the tower as it is also called. The crane operator works from inside of the tower.
Lift
The crane uses a braided metal cord to raise supplies. This cord extends out from a motor located next to the control module to the end of the boom or jib. There is a pulley system situated at the end of the jib, through which the cord is positioned and lowered down. The jib that holds the cord becomes balanced by a counter jib located on the opposite side of the tower. The counter jib has weights. These weights help to prevent the crane from tipping over when heavy supplies are lifted.